microprofile-expert

microprofile-expert

Keyword: microprofile | Platforms: gemini,claude,codex

MicroProfile Expert Skill - Deep knowledge of Eclipse MicroProfile specifications for building cloud-native microservices.

Core Mandates

• Config Externalization: All environment-specific values must use @ConfigProperty, never hardcode.
• Health Probes: Always implement both @Liveness and @Readiness checks for container orchestration.
• Metrics Exposure: Expose application metrics via @Timed, @Counted, @Metered for observability.
• API Documentation: Auto-generate OpenAPI specs from code annotations.
• Fault Tolerance: Use @Retry, @CircuitBreaker, @Timeout, @Fallback for resilient services.
• Security First: Use MicroProfile JWT for stateless authentication in microservices.

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MicroProfile Config

@ConfigProperty

@ApplicationScoped
public class PaymentConfig {

    @ConfigProperty(name = "payment.timeout", defaultValue = "30")
    int timeoutSeconds;

    @ConfigProperty(name = "payment.gateway.url")
    String gatewayUrl;  // Required - fails if missing

    @ConfigProperty(name = "payment.api-key")
    Optional<String> apiKey;  // Optional

    @ConfigProperty(name = "payment.features")
    Optional<List<String>> features;  // Comma-separated list

    @ConfigProperty(name = "payment.enabled", defaultValue = "true")
    boolean enabled;
}

Config Sources Priority

1. System properties (-Dpayment.timeout=60)
2. Environment variables (PAYMENT_TIMEOUT=60)
3. application.properties / application.yaml
4. META-INF/microprofile-config.properties
5. Custom ConfigSource implementations

Custom ConfigSource

@Priority(400)
public class DatabaseConfigSource implements ConfigSource {

    @Override
    public Map<String, String> getProperties() {
        // Load from database
        return Map.of(
            "db.host", "postgres.internal",
            "db.port", "5432"
        );
    }

    @Override
    public String getValue(String propertyName) {
        return getProperties().get(propertyName);
    }

    @Override
    public String getName() {
        return "DatabaseConfigSource";
    }

    @Override
    public int getOrdinal() {
        return 400;  // Higher = higher priority
    }
}